Dynamic metrology schemes and sampling schemes for advanced process control in semiconductor processing

ABSTRACT

Systems, methods and mediums are provided for dynamic adjustment of sampling plans in connection with a wafer (or other device) to be measured. A sampling plan provides information on specific measure points within a die, a die being the section on the wafer that will eventually become a single chip after processing. There are specified points within the die that are candidates for measuring. The stored die map information may be retrieved and translated to determine the available points for measurement on the wafer.  
     The invention adjusts the frequency and/or spatial resolution of measurements when one or more events occur that are likely to indicate an internal or external change affecting the manufacturing process or results. The increase in measurements and possible corresponding decrease in processing occur on an as-needed basis. The dynamic metrology plan adjusts the spatial resolution of sampling within-wafer by adding, subtracting or replacing candidate points from the sampling plan, in response to certain events which suggest that additional or different measurements of the wafer may be desirable. Where there are provided a number of candidate points in the die map in the area to which points are to be added, subtracted, or replaced, the system can select among the points. Further, the invention may be used in connection with adjusting the frequency of wafer-to-wafer measurements.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial No. 60/322,459, filed Sep. 17, 2001, which isexpressly incorporated herein by reference; and U.S. ProvisionalApplication Serial No. 60/298,878, filed Jun. 19, 2001, which isexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention concerns computer-related and/or assistedmethods, systems and computer readable mediums for metrology duringprocess control. More specifically, it relates to dynamic adjustment ofmetrology schemes and sampling during advanced process control methods,for example during control of semiconductor technology manufacture.

[0004] 2. Related Art

[0005] In the wafer fabrication art, measurements are made by metrologytools on wafers as they are being manufactured by processing devices, inorder to ensure that the wafers are produced according to a predefinedspecification. The measurements are made of physical properties such asfilm thickness and uniformity, dopant concentration, gate length andcritical dimension. This is known as the science of “metrology.”

[0006] Measurements to be made are typically specified in a “die map”.The die map indicates where the different chips (or die) are located ona wafer (in the typical situation where multiple chips are formed on andeventually cut from a single wafer), as well as significant locations,such as corners, on each die. In order to measure the right hand corneron each die, for example, multiple points are measured on the wafer inaccordance with the die map. Ordinarily a die map is a digitalrepresentation of coordinate points, or “metrology coordinates,” on thewafer.

[0007] The metrology coordinates are usually provided by an engineer,and vary depending on the engineer's preferences. Metrology coordinatesare conventionally provided as x, y coordinates.

[0008] A “sampling plan,” alternatively referred to as a “metrologyplan,” contains metrology coordinates drawn from the die map. Thesampling plan denotes a specific plan for taking certain measurements.These measurements may include some or all of the possible points and/orchips in the die map.

[0009] A conventional metrology system assigns a sampling plan thatpredetermines which wafers are to be measured in connection with aprocessing device, and the measurements which are to be taken of thosewafers by the metrology tool. For example, the sampling plan mightdefine that each fifth wafer should be measured at pre-designatedlocations. These sampling plans are not changed after being initiallyassigned, and hence the metrology systems are static.

[0010] Unfortunately, manufacturing results tend to drift away from theintended target or specification when there is a change in themanufacturing process, such as a change in recipe, preventativemaintenance, consumables change, environmental change or a new lot ofwafers. Conventional metrology systems tend to miss some wafers whichare outside specification limits, since these systems use a virtuallyconsistent measurement scheme, having consistently frequent measurementswith consistent spatial resolution, without taking into considerationwhether any changes were introduced into the manufacturing process whichmight change the manufacturing results.

[0011] Manufacturing systems do not typically call for a measurement ofevery wafer, since measuring takes time and increasing the number ofmeasurements results in a decrease of productivity. On the other hand,measuring fewer wafers tends to lead to delayed detection of criticalinformation for process control that may significantly impact waferyield. While conventional sampling systems will sample wafers duringand/or after production, these systems do not adjust the initiallyassigned sampling plan for the wafers during production.

[0012] Thus, there remains a need for dynamic metrology to improve thequality of products. For semiconductor wafers, there remains a need tobetter check whether each specification is met under productionconditions. There also remains a need to respond to a change inparameters which may cause a variance from intended target results, suchas recipe parameters, and to adjust the frequency and/or spatialresolution of measurements. Unfortunately, taking measurements takestime, and most processing devices are faster than the measurements thatneed to be taken by metrology tools in order to characterize the wafersusing a metrology. Thus, there remains a need for a method, system andmedium to react to changes potentially affecting the system results, andto appropriately adjust, increase, or decrease the measurementsaccordingly.

SUMMARY OF THE INVENTION

[0013] The present invention alleviates the problems of the conventionaltechniques described above by dynamically determining whether a waferneeds to be measured for process control based on changes in theresources, recipes, etc. In addition, for a given wafer to be measured,measuring points are also dynamically assigned to the metrology tool.

[0014] More specifically, two variations of embodiments of the presentinvention are contemplated and may be used independently or together.According to the first variation, the frequency at which wafers aremeasured (“wafer-to-wafer”) is adjusted, following an event thatsuggests that more (or fewer) wafers should be measured. According tothe second variation, the spatial resolution of the measurements ofthose wafers selected for measurement (“withinwafer”) is increased ordecreased, following an event that suggests each wafer which is measuredshould be measured in greater (or lesser) detail.

[0015] In one or more embodiments of the present invention, candidatecoordinate measurement points are mapped in a die map, and a subset ofthe candidate coordinate measurement points are selected as the initialpoints where measurements are to be made. Subsequently, according to thewithin-wafer variation, the invention dynamically selects more, fewer ordifferent points (depending on the circumstances) to be measured fromamong the candidate coordinate measurement points. According to thewafer-to-wafer variation, when there is a change in the manufacturingprocess, the number of measurements may be increased, to measure everywafer rather than just every third wafer for example. As one example,when a new recipe is implemented to significantly change the thicknessat a particular region on the wafer, a greater number of within-wafermeasurements can be made at that location by selecting more and/ordifferent candidate measurement points. As another example, when a faultis detected, the frequency of wafers selected for measurement isincreased; this increases the probability of detecting defectivelymanufactured wafers and correcting the control parameters (such as inconnection with a feed forward/feedback method). In some situations,large deviations may require less frequent measurement or less spatialresolution than small deviations when the large deviations clearlyidentify the problem, whereas small deviations may be difficult toidentify and more frequent and/or dense measurements may be necessary.The reverse may be appropriate in other situations regarding thefrequency and density of measurements, or it may be the case that thesame number of measurements may be taken regardless of deviation.

[0016] According to one or more embodiments of the present invention,there is provided a method, system and/or computer-implemented methodfor measuring at least one manufacturing characteristic for at least oneproduct manufactured by a manufacturing process. Information isprovided, representative of a set of candidate points to be measured bythe manufacturing process on the at least one product. The manufacturingprocess executes a plan for performing measurements on the at least oneproduct to measure the at least one manufacturing characteristic, theplan defining the measurements to be made responsive to the set ofcandidate points. A change in the manufacturing process is detected, thechange including at least one of: receiving new material in themanufacturing process, detecting a fault in the manufacturing process,detecting a change in a control parameter in the manufacturing process,and detecting a variation in a measurement of the at least one product.

[0017] According to one or more embodiments, the plan for performingmeasurements is adjusted based on the detected change and at least oneadditional measurement is performed responsive thereto.

[0018] According to one or more embodiments, the measurements of theplan are adjusted wafer-to-wafer and/or within-wafer.

[0019] According to one or more embodiments, the product is asemi-conductor wafer and the manufacturing process is an automatedsemi-conductor manufacturing process.

[0020] According to one or more embodiments, the plan further includesinformation representative of a metrology recipe.

[0021] According to one or more embodiments, the candidate points areincluded in a map corresponding to the at least one product. The planmay be a pre-determined sampling plan.

[0022] According to one or more embodiments, the plan defines at leastone region on the product, each of the candidate points corresponding tothe at least one region.

[0023] According to one or more embodiments, the adjustment includesdetermining the at least one region corresponding to the detectedchange, selecting the at least one additional measurement responsive tothe candidate points corresponding to the determined region, assigningthe selected at least one additional measurement to be performed underthe plan, and revising at least one of the measurements, the additionalmeasurement and the plan. The adjustment may include determining whetherthe detected change may affect a series of products, and if so,determining whether to measure at least one of the products in theseries of products. The products may be provided in a group, and theplan may further include first information representative of theproducts in the group that are available to be measured, and secondinformation representative of the products in the group that are to bemeasured under the plan.

[0024] According to one or more embodiments, information representativeof measurement results on the product is discarded when the measurementsresults indicate a variation in measurement of the product and/or when afault is detected in the manufacturing process.

[0025] According to one or more embodiments, the sampling plan includesa plurality of splines radiating from a center of a product, and thecandidate points are distributed along the splines. The distribution ofthe candidate points along the splines may be weighted according to asurface area of the product. According to one or more other embodiments,the sampling plan includes a plurality of radially distributed candidatepoints.

BRIEF DESCRIPTION OF THE FIGURES

[0026] The above mentioned and other advantages and features of thepresent invention will become more readily apparent from the followingdetailed description in the accompanying drawings, in which:

[0027]FIG. 1 is a flow chart showing one example of dynamic metrologyfor “wafer-to-wafer” processing in the present invention.

[0028]FIGS. 2A and 2B are an illustration of regions on a wafer, withFIG. 2A being a plan view of the wafer and FIG. 2B being a cross-sectionof the wafer along radius B-B of FIG. 2A.

[0029]FIG. 3 is a flow chart showing one example of dynamic metrologyfor “within-wafer” processing in accordance with one or more embodimentsof the present invention.

[0030]FIGS. 4A and 4B are a spiral sampling plan for a wafer for usewith one or more embodiments of the invention, with FIG. 4A being a planview of the wafer and FIG. 4B being a cross-section of the wafer along aradius of FIG. 4A.

[0031]FIG. 5 is an example of another sampling plan for use with one ormore embodiments of the invention.

[0032]FIG. 6 is a block diagram of a computerized process control systemwhich may be used in connection with one or more embodiments of thepresent invention.

DETAILED DESCRIPTION

[0033] The following detailed description includes many specificdetails. The inclusion of such details is for the purpose ofillustration only and should not be understood to limit the invention.Throughout this discussion, similar elements are referred to by similarnumbers in the various figures for ease of reference. In addition,features in one embodiment may be combined with features in otherembodiments of the invention.

[0034] In one or more embodiments of the present invention, staticmetrology means there is a pre-determined sampling plan in connectionwith a wafer (or other device) to be measured, specifying substantiallythe same points for each wafer (or the other device). In contrast, adynamic metrology plan utilizes an initial sampling plan and adjusts thesampling responsive to certain events or non-events. As an example of anadjustment due to a non-event, if the last ten wafers measured are allthe same, and if the processing device did not change, and if the recipeon the processing device did not change, one could reasonably assumethat the next series of wafers will have measurements that are also allthe same. That being the case, then in order to increase throughput anddecrease the time it takes to do measurements, the invention providesfor dynamically adjusting the measurements, for example, such that everythird wafer instead of every wafer is measured. This invention thusdetects and adjusts for not only potential errors, which could arise forexample upon a recipe change, but also for accuracy.

[0035] One or more embodiments of the present invention contemplate thatthe invention may be used in connection with wafer-to-wafer measurementsdescribed above, as well as, or alternatively, in connection withwithin-wafer measurements. Consider an example of within-wafermeasurements, in which measurements are taken along a radius of a 200 mmdiameter wafer and the radius is measured in 10 mm increments. Duringprocessing it is noted or detected by the usual detection process thatthere is a large variation at the 50 mm and 60 mm points. For the nextsample, the system adjusts to measure another point from the samplingplan between 50 mm and 60 mm to better characterize that variation, oroptionally to measure an additional point, for example, between 40 mmand 50 mm that is near the location of the variation. If the die mapincludes points at 45 mm and 55 mm, these points can then be added asmeasurement points. Adjusted measurements now encompass in this example,40 mm, 45 mm, 50 mm, 55 mm, and 60 mm. The system dynamically added thetwo additional points (in the example) to better characterize themeasurement and/or the variation. Where there are provided a number ofcandidate points in the die map allowing points to be added orsubstituted, the system can select among the points any of several ways,such as selecting the closest to mean, mode, other statistical analysis,etc.

[0036] A sampling plan provides specific measure points within a die, adie being the section on the wafer that will typically eventually becomea single chip after processing. There are specified points within thedie that are candidates for measuring. The map of the die is stored,preferably in an electronic format representing the map. One appropriateplace for storing the die map information is in the factory automationsystem (“MES” or manufacturing execution system). The stored die mapinformation may be advantageously retrieved and translated to determinethe available points for measurement on the wafer. Referring back to theprevious example proposing measurement points on the radius at 45 mm and55 mm, if these specific points are not relevant to the current die(e.g., they are not specified by the die map), an appropriatereplacement would be points selected from the candidate points specifiedby the die map which are close to or between 45 mm and 55 mm. Thosepoints could be selected dynamically as well. Other criteria may be usedfor selecting points as well.

[0037] Dynamic metrology is performed to better meet a certainspecification. For example, if recipe parameters are changed on theprocessing device, to adjust the thickness of a film that is depositedon the wafer, it may be desirable to more closely check whether thespecification is still being achieved by performing measurements.

[0038] In order to avoid slowing down the process, one or moreembodiments of the present invention advantageously determine theappropriateness of performing additional measurements when one or moreevents occur that are likely to indicate an internal or external changeaffecting the manufacturing process or results. The increase inmeasurements and possible corresponding decrease in processing occur onan as-needed basis and/or based on predetermined criteria.

[0039] The wafer-to-wafer variation of the invention, for example, cancheck for events which may affect a series of wafers and may adjust thesampling plan. For example, during processing, the system determines ifan increase is needed in the frequency of wafers measured for processcontrol, for example, based on 1) a change in the processing device thewafers are processed on, 2) a change in the parameters or recipe thatwere used by the processing device to process the wafer, 3) largedetected variations or errors in measurements, and/or 4) a significantrun of wafers without errors.

[0040] Particularly regarding within-wafer variation, one or moreembodiments of the present invention contemplate that the system obtainsa stored die map with metrology coordinate information from the MES. Asindicated, the system can provide not only for assigning the measurementpoints optionally dynamically, but also for de-assigning.

[0041] One or more embodiments of the present invention envisionchanging the sampling plan using information that is gathered from theMES and automatically using that new sampling plan, depending on, forexample the type of processing device on which the wafers are processed.Advantageously, the system has stored information about a wafer thatindicates, among other things, the type of chip or type of device and anassociated sampling plan to be used when measuring a wafer containing aspecific device. Based on the type of device, the associated samplingplan or die map can be obtained, where the die map includes a set ofcandidate metrology points. The system then selects metrology points forthe current wafer from the set of, or responsive to, the candidatepoints in the die map.

[0042] With respect to the sampling plan, generation of the samplingplan can vary from device to device (chip type to chip type) and somemeasurements may be based on die distribution on the wafer. By dividinga wafer into regions and using regions of the wafer for measurement, oneor more embodiments of the present invention provide flexibility inselecting one or more points from available points in the region. Use ofregions is one way to provide a pool of candidate points, from which thesystem may select points that are most relevant to the desiredinformation about the film on the wafer.

[0043] In practice, the system may, for example, measure twenty-two totwenty-five points per wafer from the pool of candidate points. For someprocesses the system might measure fewer points, such as eight points,because it takes longer to measure those points or the wafer processingtime is faster. For other processes the system might measure one pointof another type of property, such dopant concentration, which is arelatively slow measurement.

[0044] In any event, it is important to balance the time consumed in ameasurement against the need to produce quality products. Manufacturersconsider it to be more important to be within specifications and notproduce defective product, than to rapidly produce product of suspectqualities.

[0045] Each processing device on which a wafer is processed has adifferent processing time, and therefore the selected standard samplingrate may depend on the speed of processing of the processing device andmetrology tool. On some processing devices, measurements on every waferwill not slow down processing since the speed of the processing deviceis slower than the measurements by the metrology tool. For example,polishing and cleaning processing devices may consume five minutes ormore to process a wafer. In that case a post-processing measurement bythe metrology tool on every wafer would often not reduce throughput.

[0046] Additionally, the system may determine whether or not to makeadditional measurements based on the initial and the final condition ofthe wafers. For example, if there is a situation in which the incomingthickness profile of a cross section of a wafer does not change verymuch, the system may reduce the frequency of samples of incomingprofiles, wafer-to-wafer. On the other hand, if the incoming profile ischanging significantly, it may be desirable to measure every enteringwafer.

[0047] Reference is made to FIG. 1, illustrating an example of a flowchart for one or more embodiments of a wafer-to-wafer dynamic metrologysystem. The system checks whether there may have been a significantchange in the state of the processing device, which can be detected bychecking, for example, idle time, change of consumables, etc. There maybe other events that could be checked that would indicate a potentialchange in the processing device or lead one to believe that it mighthave been changed. It is possible that the processing device itself mayinclude sufficient programming to recognize or track those type ofevents. The flowchart example in FIG. 1 includes an example set ofevents or state changes that initiate analysis and decision making,based upon information gathered from the processing device and based ona significant internal or external change (e.g., system was idle for along time, chamber was cleaned, new batch of slurry, initial wafer,etc.). Other events or states may be included in the set from which itis determined whether or not to measure a wafer.

[0048] One or more embodiments, of the present invention also envisionthe following. Assume that there is provided an initial sampling plan.The plan could, for example, direct measuring of specific points on eachwafer and/or comprise information indicating which wafers within the lotwill be measured. The wafer is measured according to the sampling plan.According to the wafer-to-wafer metrology plan, the system deviates fromthe initial sampling plan when warranted. The system could return to theinitial sampling plan once it detects that the process is again “normal”or again producing product within specification.

[0049] Referring still to FIG. 1, consider for example a typicalcassette of twenty-five wafers to be processed according to one or moreembodiments of the present invention. The cassette of wafers arrives atthe processing device, usually from some other processing device, andprocessing on the lot is started, at block 101.

[0050] If a wafer being processed by a processing device is the firstwafer of a particular lot on the processing device then it may bedesirable to measure this wafer, in order to detect if perhaps there wassome processing device related property that changed. Thus, at block103, the system checks whether it is processing the first wafer on theresource. This could also include situations such as followingpreventative maintenance where the chamber in the processing device hasbeen cleaned or perhaps a consumable was replaced in the processingdevice.

[0051] If a processed wafer was the first (or other predetermined) waferon the resource in accordance with block 103, then the system checks atblock 105 whether the processing device was idle, greater than somespecified time before starting the present process; and if theprocessing device was not significantly idle, the system checks at block107 whether the process was changed or altered. If the process was notchanged, a measurement of the wafer may or may not be implementedaccording to the initial sampling plan at block 116; the wafer isaccordingly measured at block 120 or not measured at block 118. On theother hand, if the resource was idle for a sufficiently long time, or ifthe process has changed, at blocks 109 or 111 respectively, a newmeasurement is taken.

[0052] If the wafer was not the first one on the processing device, thenas indicated, at block 113, the system checks whether a significantchange was made to the recipe, such as by the process control algorithmor process controller. It is typically desirable to ensure that even ifa significant change was made, the specifications are still satisfied. Achange to the recipe could include time, pressures, flow rates, etc., oreven a completely different recipe. If the recipe was significantlychanged, then at block 115, the system calls for a measurement of thewafer.

[0053] The system also checks whether a fault was detected, such as inthe processing device. Processing devices may be monitored by thefactory automation system, for example to determine whether there issome problem with the processing device, either from the automationsystem side or from the processing device itself. Also, the processingdevice itself may include the ability to detect a fault. If a fault isdetected, the system could subsequently measure to confirm that thewafer is within specifications. Thus, at block 117, it is determinedwhether a fault was detected. If a fault was detected, at block 123 thesystem measures the wafer. Since it is likely that the wafer has errors,it might be desirable not to use such measurements for feedbackpurposes.

[0054] There may be two cases for uses of measurement values. In thefirst case, the system uses the measurement value or stores thatmeasurement value for further processing, such as measurements followinga resource idle condition. In the second case, such as following a faultdetection, the system may check the wafer or series of wafers foracceptability but does not store the value which might skew historicalresults. In the first case, the system is using the historical value formodeling of the processing device in order to better predict how theprocessing device will behave, or for other purposes. For example, wherea fault is know to have occurred, the manufacturer will want to find andcorrect the cause of the fault, often by changing a process component orparameter. Thus, the process data attributed to a wafer that triggereddetection of a fault is not indicative of the “normal” processing in theprocess system. On the other hand, for the fault detection case, thesystem merely ensures that that wafer is a good (e.g., usable) waferversus a bad wafer. Unfortunately, usually following a fault there areseveral wafers in a series potentially affected by the fault, and it isdesirable to measure the wafers in the series. Once the wafer(s) aremeasured following a fault, if the wafer(s) are bad, it is desirable tomark the wafer as questionable and discard the measurement value as wellas perhaps the wafer itself.

[0055] Similarly, if a wafer is off target despite no change to therecipe, no detection of a fault, and no other likely cause of error,there is likely to be a series of off-target wafers. Consequently, wherea wafer with errors is detected, the next wafer is significantly morelikely to also experience errors. Thus, at block 119, the system checkswhether the previous wafer was sufficiently far from the target, asdetermined by a previous measurement made in accordance with FIG. 1. Ifso, then at block 121 the system measures the current wafer as well.

[0056] Finally, it may be desirable to measure the wafer according tothe initial sampling plan. Thus, at block 125, the system checks theinitial sampling plan to advantageously determine whether the currentwafer should be measured according to the initial sampling plan. If not,then the system does not measure the wafer. According to one or moreembodiments, a modified sampling plan is used to measure the wafer underappropriate situations, such as after a change of type of chip.

[0057] Similarly, if no conditions affecting wafer processing arechanged, and if the series of wafers have been on target, one wouldexpect the wafers to continue to be on target. Thus, as indicated atblock 127, if the measurement of the last n wafers were sufficiently ontarget, there is no need to measure the wafer in this instance or asfrequently. In this manner, the number of measurements can be reducedand processing time is potentially reduced. On the other hand, if atblock 127 the system determines that the last series of n wafers werenot on target, at block 129 the system measures the current wafer.

[0058] Reference is made to FIG. 2, a map of a wafer illustratingmeasurement regions for the within-wafer dynamic metrology. It isreferred to as “within-wafer” since the system may be changing themetrology within the wafer, in distinction to the previously-describedwafer-to-wafer dynamic metrology. (FIG. 3, described in detail below,illustrates an example of a flow chart for within-wafer dynamicmetrology.)

[0059] Where the process performed by the processing device on the waferis symmetric such that the system is affecting portions of the film onthe wafer in a symmetric matter, it may be reasonable to measure fewerpoints, perhaps a measurement of only one radii. On the other hand,where there were previous steps performed by the processing device onthe wafer that were asymmetric, information on additional measurementvalues may need to be captured. The number of desirable measurementpoints therefore additionally depends upon the type of process, and uponthe step in the process if applicable.

[0060] For instance, given a very uniform process, perhaps only fivepoints on the wafer need to be measured to provide sufficient precision.On the other hand, given a very non-uniform process or much unresolvedinformation, perhaps twenty-five points should be measured to achieve asufficient level of precision.

[0061] Typically the factory automation system, or the software in thefactory automation system, is programmed to determine which process (orprocesses) or step within a process is being run on which processingdevice. Based on that information, the system can determine whether fewor many points are desired for an adequately precise measurement or setof measurements of the wafer.

[0062] Consider, for example, a processing device with multiple chambersor resources independently processing wafers. In this example, theprocess control algorithm describes four recipe changes. The inventiondetermines which wafers need to be measured (wafer-to-wafer), and anydesired change in number of measurement points due to the dynamic recipechange (within-wafer). This metrology strategy consequently enables adynamic metrology change based on the die map from the MES or otherfactory automation system.

[0063] The die map provides a pool of candidate points corresponding toa wafer to be measured, and the system can select from among thecandidate points, the points that correspond most directly to theinformation needed or desired in connection with that wafer. The MES orother factory automation system provides information indicatingallowable or relevant possible points that could be measured; from thosecandidate points, one or more embodiments of the present inventioncontemplate that the system selects the minimal set of points that wouldcapture the desired information.

[0064]FIGS. 2A and 2B illustrate a plan view and a cross section of anexample of a typical wafer 201, in this instance having radial regions 1through 5. As shown in FIG. 2A, the illustrated wafer 201 is circular.Chips on the wafer are usually square and placed across the wafer. Atthe end of processing, the chips are divided from the wafer. FIG. 2Bshows a cross section of the wafer of FIG. 2A, across section B-B fromone edge to the center of the wafer. Region 1 extends radially from thecenter to 40 mm; region 2 extends from 40 mm to 60 mm; region 3 extendsfrom 60 mm to 80 mm; region 4 extends from 80 mm to 92 mm; and region 5extends from 92 mm to 95 mm. A wafer could be divided into more or fewerregions. Also, although the regions are illustrated as radial, the sameconcepts apply where the regions are neither circular nor radial.

[0065] A die map includes a sampling plan that optionally distinguishesamong different regions of the wafer. Such a sampling plan would includeinformation indicating a set of measurement points, associated withregions of the wafer.

[0066] The flowchart of FIG. 3 discusses an example of within-wafermetrology, that is, when the system should or should not change themeasurement points. FIG. 3 thus contrasts to FIG. 1, indicating whetherto measure a current wafers (wafer-to-wafer dynamic metrology). FIG. 3defines an example set of questions to determine whether more points areneeded to measure a region variation within a given wafer.

[0067] Reference is now made to FIG. 3, illustrating an example of thewithin-wafer dynamic metrology, as contemplated by one or moreembodiments of the present invention. At block 301, the wafer ismeasured by the metrology tool utilizing the current sampling plan.Having measured the wafer, the system analyzes the current wafer todetermine whether there are significant variations that might warrantchanging the sampling plan for the next wafer. The wafers arepotentially changed from run to run. That is, the system performs anaction, and then based upon the results of that action, the systemdetermines whether to utilize the same sampling plan for the next waferor to do something different.

[0068] At block 303, it is determined whether there is a variation fromthe specification within one or more of the regions on the currentwafer. If not, then as indicated by block 305 there is no need to addmore sampling points.

[0069] At block 307, if there was a variation in a region, it is thendetermined whether the variation was due to an outlier or flier. Anoutlier or flier is a situation in which the measurement point is not anaccurate reflection of the actual value. If there is a speck of dust onthe wafer, for example, this may cause an erroneous thicknessmeasurement; or for instance the actual measured point may besignificantly distant from the correct measurement coordinates,resulting in significantly higher or lower thickness. An outlier orflier can be determined statistically in a number of ways based on howdifferent the measured point is from the expected measurement. It may bedifficult to determine in some cases whether the variation is due to aflier or if there is an actual variation. The data collected could beused to indicate a potentially defective die.

[0070] Of course, it should be understood that one or more embodimentsof the present invention contemplate that any number of other causes forvariations can be detected, and a decision made accordingly as towhether (and how) the sampling plan may be changed.

[0071] Referring still to FIG. 3, if the variation from thespecification is due to an outlier or flier, then as indicated by block309, the sampling plan is not changed. The measurement is not likely tobe an accurate reflection of the wafer, and therefore the system shouldnot react to the measurement.

[0072] At block 311, it is determined whether the variation from thespecification is one for which the processing device can possiblycompensate. For example, a processing device may be able to correct forradial variation, but not for a variation that is angular or azimuthal.Thus, at block 313, if the processing device cannot compensate for thevariation in the region, then the sampling plan is not changed. On theother hand, if the processing device can compensate for the variation inthe region, then at block 315 points are added to the region in thesampling plan for the next wafer in order to better characterize theregion. Optionally, the data may be fed back to system controller inorder to change the process in response to this drift condition.

[0073] According to one or more embodiments of the inventions, an errorin one or more wafers may initiate some level of error handling and/oralarming. If there is an error that does not result in a change to thesampling plan, such as a non-systematic variation, and even if thesystem cannot compensate, in one or more embodiments of the presentinvention the system might generate an alarm or trigger performance ofother error handling. If the error exhibits the characteristics of asystematic effect, such as wafers out of specification, then an alarmcould be generated. If the error is one wafer that is out ofspecification, according to one or more embodiments of the invention,the system flags that wafer.

[0074] The flow chart of FIG. 3 illustrates one potential example ofwithin-wafer metrology. Other types of checks and decisions are alsocontemplated and may be used in combination with, and/or replace, thedetailed checks. For example, an additional check could include whetherthere is a large change in the recipe parameter that could have affecteda specific region; if so, a determination can be made as to whether thechange affected the region to the extent that more information isdesirable; and if so, more metrology points can be added to the samplingplan.

[0075] Reference is now made to FIGS. 4A and 4B, illustrating a planview and sectional view, respectively, of a triangular spiral samplingplan. This is one example of a specific sampling plan, showing specificmeasurement points 401 in relation to a wafer 201. Other static samplingplans may be used. Nevertheless, the illustrated spiral sampling plan iswell adapted to capturing both radial change as well as angular change.Consider polar coordinates, where R is the radius and theta is theangle; the triangular spiral sampling plan can capture variations inboth the R direction and the theta direction. If the system cancompensate only for variations that are radial, it may be desirable toadd measurement points in the radial direction. Even if a significantangular variation was detected, one might not add any measurement pointsif the variation cannot be corrected anyway due to the manner of holdingand/or spinning the wafer in the processing device.

[0076] Still referring to the example sampling plan illustrated in FIGS.4A and 4B, the points 401 are distributed along three splines 403radiating from the center of the wafer. The points 401 of this exampleare generally distributed in each of eight regions, shown in FIG. 4B. Inthis sampling plan one could potentially add points in a radialdirection. There could be provided more or fewer regions in otherembodiments of the invention. Suppose that in Region 1, which are allpoints radially from approximately 0 mm to 40 mm, there is a largevariation; more measurement points could be added from the die map inorder to better characterize that variation. FIG. 4A indicatesequidistant radii at 24.375 mm from the center, 48.75 mm, 73.125 mm, and97.5 mm for purposes of illustration. It should be noted that thedistance between points 401 along spline 403 advantageously decreasestowards the outer diameter of the wafer, to accommodate the increase inthe surface area in relation to the width of the region.

[0077]FIGS. 4A and 4B illustrate only one of many potential samplingplans, in this instance a particular spiral sampling plan. Othersampling plans are possible. One advantage of the illustrated spiralsampling plan is that it quantifies not only radial but also angularvariation. Another advantage is that it also measures a weighted region,that is it measures a selected number of coordinates in approximateproportion to the wafer surface area that they represent. Closer to theedge of the wafer, measurement points are more dense or closer together,since the radial distance is much further and the area of the region isgreater in comparison to the width of the region.

[0078] Moreover, the variation on the edge typically will be much higherthan variation toward the center of the wafer. The variation tends toincrease proportionately further away from the center. As a result, thedensity of the points to be measured may be advantageously increased asthe points move radially outward.

[0079] Furthermore, the present invention optionally optimizes themeasuring speed of the spiral sampling plan. In performance ofmetrology, a measurement is faster if performed radially across thewafer. According to the spiral sampling plan contemplated by one or moreembodiments of the present invention, the wafer may be rotatedapproximately 120 degrees subsequent to a linear measurement, and thenthe next measurement is taken at the next point positioned radiallyacross the wafer; then the wafer is again rotated approximately 120degrees for the next measurement and so forth. The angle of rotation canbe varied to correspond to the disposition of points as well as toaccommodate the capabilities and/or limitations of the metrology tool.The wafer may be positioned on a pedestal and rotated and shifted whilethe metrology tool performs the measurement of the wafer.

[0080] Other sampling plans are also contemplated by one or moreembodiments of the present invention, including a sampling plan with alarge number of points, such as forty-nine (illustrated in FIG. 5), or asmall number of points, such as five. Other sampling plans with otherdistributions of metrology points, such as distributed in concentriccircles or star formations, or other variations may be used in one ormore embodiments.

[0081] Reference is made to FIG. 6, illustrating a possible computerizedprocess control system which may be used in connection with one or moreembodiments of the present invention. The system includes a standardfactory automation system such as an APC 601. The APC 601 provides forcentral control of, and communication with, one or more standardprocessing devices 603 or resources. In turn, the processing device 603communicates with and controls a standard metrology tool 605, whichmeasures wafers in accordance with the processes described in connectionwith the present invention. Although FIG. 6 illustrates a typicalsystem, other configurations are possible, such as having the metrologydevice(s) 605 communicate with the APC 601, or even omitting the APC 601and having the metrology device 605 pattern the processes describedherein.

[0082] Examples of processing devices that may be used in conjunctionwith the invention include chemical mechanical planarization (CMP)tools, etch tools, chemical vapor deposition (CVD) tools, lithographytools and others. It should be noted that the processing device mayincorporate the metrology tool in some configurations.

[0083] While this invention has been described in conjunction with thespecific embodiments outlined above, many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the preferred embodiments of the invention as set forth areintended to be illustrative and not limiting. Various changes may bemade without departing from the spirit and scope of the invention asdefined in the following claims.

[0084] For example, it would be possible to use any sampling plan withthe invention. A sampling plan may include information in addition tothat mentioned above. Further, a sampling plan may combine informationfrom multiple sampling plans. As another example, although the abovediscusses a pre-determined or static sampling plan, such pre-determinedor static sampling plan includes those sets of coordinate pointsmeasured on the fly such as just prior to wafer processing.

[0085] As another example, events or conditions in addition to, incombination with, and/or replacing these discussed above, could bechecked as part of the wafer-to-wafer metrology determination. Forexample, a metrology tool, a processing device, or the system itselfcould indicate a fault. Moreover, it is possible that the reason for thefault could be indicated, and such information could be specificallychecked and appropriately handled as well. The system could check forchanges to the recipe in several different ways, such as replacement ofa recipe, or change in recipe parameters.

[0086] Similarly, other events or conditions could be handled as part ofthe within-wafer determination. For example, there may be one or moreregions of any shape on the wafer. As another example, points could beomitted from the sampling plan in appropriate cases. A further exampleincludes other events mentioned above in connection with wafer-to-waferprocessing.

[0087] As another example, the factory automation system may be ageneral purpose computer, or a specially programmed special purposecomputer. It may also be implemented as a distributed computer systemrather than as a single computer; some of the distributed system mightinclude embedded systems. Further, the programming may be distributedamong processing devices and metrology tools or other parts of theprocess control system. Similarly, the processing could be controlled bya software program on one or more computer systems or processors, orcould be partially or wholly implemented in hardware. Moreover, thefactory automation system may communicate directly or indirectly withthe relevant metrology tool(s), processing devices, and metrologysystem(s); or the metrology tool(s), processing devices and metrologysystem(s) may communicate directly or indirectly with each other and thefactory automation system.

What is claimed is:
 1. A computer-implemented method of measuring atleast one manufacturing characteristic for at least one productmanufactured by a manufacturing process, comprising the steps of: (A)providing information representative of a set of candidate points to bemeasured by the manufacturing process on the at least one product; (B)executing, by the manufacturing process, a plan for performingmeasurements on the at least one product to measure the at least onemanufacturing characteristic, the plan defining the measurements to bemade responsive to said set of candidate points; (C) detecting a changein the manufacturing process, the change including at least one of:receiving new material in the manufacturing process, detecting a faultin the manufacturing process, detecting a change in a control parameterin the manufacturing process, and detecting a variation in a measurementof the at least one product; and (D) adjusting the plan for performingmeasurements based on the detected change.
 2. The method of claim 1,further comprising the step of performing at least one additionalmeasurement, responsive to the detected change.
 3. The method of claim1, wherein the step of adjusting further includes adjusting themeasurements of the plan wafer-to-wafer and/or adjusting themeasurements of the plan within-wafer.
 4. The method of claim 1, whereinthe product is a semi-conductor wafer and the manufacturing process isan automated semi-conductor manufacturing process.
 5. The method ofclaim 1, wherein the plan further includes information representative ofa metrology recipe.
 6. The method of claim 1, wherein the candidatepoints are included in a map corresponding to the at least one product.7. The method of claim 1, wherein the plan is a pre-determined samplingplan.
 8. The method of claim 1, wherein the plan defines at least oneregion on the product, each of the candidate points corresponding to theat least one region.
 9. The method of claim 8, wherein the step ofadjusting includes determining the at least one region corresponding tothe detected change, selecting at least one additional measurementresponsive to the candidate points corresponding to the determinedregion, assigning the selected at least one additional measurement to beperformed under the plan, and revising at least one of the measurements,the additional measurement and the plan.
 10. The method of claim 1,wherein the step of adjusting includes determining whether the detectedchange may affect a series of products, and if so, determining whetherto measure at least one of the products in the series of products. 11.The method of claim 10, wherein there is provided a plurality ofproducts including the at least one product, being provided in a group,and wherein the plan further includes first information representativeof the products in the group that are available to be measured, andsecond information representative of the products in the group that areto be measured under the plan.
 12. The method of claim 1, furthercomprising the step of discarding information representative ofmeasurement results on the at least one product when the measurementsresults indicate a variation in measurement of the at least one productand/or when a fault is detected in the manufacturing process.
 13. Themethod of claim 7, wherein the sampling plan includes a plurality ofsplines radiating from a center of the at least one product, and/orwherein the candidate points are distributed along the splines.
 14. Themethod of claim 13, wherein a distribution of the candidate points alongthe splines is weighted according to a surface area of the at least oneproduct.
 15. The method of claim 7, wherein the sampling plan includes aplurality of radially distributed candidate points.
 16. Acomputer-implemented method of measuring at least one manufacturingcharacteristic for at least one semi-conductor wafer manufactured by anautomated semi-conductor manufacturing process, comprising the steps of:(A) providing information representative of a set of candidate points tobe measured by the manufacturing process on the at least one wafer, theset of candidate points being included in a map corresponding to the atleast one wafer; (B) executing, by the manufacturing process, apre-determined sampling plan for performing measurements on the at leastone wafer to measure the at least one manufacturing characteristic, theplan defining the measurements to be made responsive to said set ofcandidate points, and the plan defining at least one region on the atleast one wafer, each of the candidate points corresponding to the atleast one region; (C) detecting a change in the manufacturing processresponsive thereto, the change including at least one of: receiving newmaterial in the manufacturing process, detecting a fault in themanufacturing process, detecting a change in a control parameter in themanufacturing process, and detecting a variation in a measurement of theleast one wafer; and (D) adjusting the plan for performing measurementsbased on the detected change and performing at least one additionallymeasurement responsive thereto; (E) wherein the step of adjustingincludes determining the at least one region corresponding to thedetected change, selecting the at least one additional measurementresponsive to the candidate points corresponding to the determinedregion, assigning the selected at least one additional measurement, andrevising at least one of the measurements, the additional measurementand the plan; (F) wherein the step of adjusting includes determiningwhether the detected change may affect a series of wafers, and if so,determining whether to measure at least one of the wafers in the seriesof wafers; (G) wherein, there is provided a plurality of wafersincluding the at least one wafer, being provided in a group, and whereinthe plan further includes first information representative of the wafersin the group that are available to be measured, and second informationrepresentative of the wafers in the group that are to be measured underthe plan; (H) discarding information representative of measurementresults on the at least one wafer when the measurements results indicatea variation in measurement of the at least one wafer and when a fault isdetected in the manufacturing process; and (I) the sampling planincludes a plurality of splines radiating from a center of the at leastone wafer, the candidate points being distributed along the splines; anda distribution of the candidate points along the splines is weightedaccording to a surface area of the at least one wafer.
 17. Acomputer-implemented system of measuring at least one manufacturingcharacteristic for at least one manufactured by a manufacturing process,comprising: (A) stored information representative of a set of candidatepoints to be measured by the manufacturing process on the at least oneproduct; (B) stored information representative of a plan for performingmeasurements on the at least one product to measure the at least onemanufacturing characteristic, the plan defining the measurements to bemade responsive to said set of candidate points; (C) a processor,detecting a change in the manufacturing process, the change including atleast one of: receiving new material in the manufacturing process,detecting a fault in the manufacturing process, detecting a change in acontrol parameter in the manufacturing process, and detecting avariation in a measurement of the at least one product; and adjusting,responsive to a detected change, the plan for performing measurementsbased on the detected change.
 18. The system of claim 17, wherein theprocessor further performs at least one additional measurementresponsive to the detected change.
 19. The system of claim 17, whereinthe processor further adjusts the measurements of the planwafer-to-wafer and/or within-wafer.
 20. The system of claim 17, whereinthe product to be measured is a semi-conductor wafer and themanufacturing process is an automated semi-conductor manufacturingprocess, further comprising at least one metrology tool for performingmeasurements on said semi-conductor wafer, operatively connected to theprocessor.
 21. The system of claim 17, wherein the plan further includesinformation representative of a metrology recipe.
 22. The system ofclaim 17, wherein the candidate points are included in a mapcorresponding to the at least one product.
 23. The system of claim 17,wherein the plan is a pre-determined sampling plan.
 24. The system ofclaim 17, wherein the plan defines at least one region on the product,each of the candidate points corresponding to the at least one region.25. The system of claim 24, wherein the measurements are adjusted bydetermining, in the processor, the at least one region corresponding tothe detected change, selecting at least one additional measurementresponsive to the candidate points corresponding to the determinedregion, assigning the selected at least one additional measurement to beperformed under the plan, and revising at least one of the measurements,the additional measurement and the plan.
 26. The system of claim 17,wherein the measurements are adjusted by determining, in the processor,whether the detected change may affect a series of products, and if so,determining whether to measure at least one of the products in theseries of products.
 27. The system of claim 26, wherein there isprovided a plurality of products including the at least one product,being provided in a group, and wherein the plan further includes firstinformation representative of the products in the group that areavailable to be measured, and second information representative of theproducts in the group that are to be measured under the plan.
 28. Thesystem of claim 17, further comprising storage of informationrepresentative of measurement results on the at least one product,except when the measurements results indicate a variation in measurementof the at least one product and/or when a fault is detected in themanufacturing process.
 29. The system of claim 23, wherein the samplingplan includes a plurality of splines radiating from a center of the atleast one product, and wherein the candidate points are distributedalong the splines
 30. The system of claim 29, wherein a distribution ofthe candidate points along the splines is weighted according to asurface area of the at least one product.
 31. The system of claim 17,wherein the sampling plan includes a plurality of radially distributedcandidate points.
 32. A computer-implemented system of measuring atleast one manufacturing characteristic for at least one semi-conductorwafer manufactured by an automated semi-conductor manufacturing process,comprising: (A) stored information representative of a set of candidatepoints to be measured by the manufacturing process on the at least onewafer, the set of candidate points being included in a map correspondingto the at least one wafer; (B) information representative of apre-determined sampling plan for performing measurements on the at leastone wafer to measure the at least one manufacturing characteristic, theplan defining the measurements to be made responsive to said set ofcandidate points, and the plan defining at least one region on the atleast one wafer, each of the candidate points corresponding to the atleast one region; (C) a processor, detecting a change in themanufacturing process responsive thereto, the change including at leastone of: receiving new material in the manufacturing process, detecting afault in the manufacturing process, detecting a change in a controlparameter in the manufacturing process, and detecting a variation in ameasurement of the at least one wafer; and adjusting, responsive to thedetected change, the plan for performing measurements based on thedetected change and performing at least one additional measurementresponsive thereto; (D) wherein the measurements are adjusted bydetermining, in the processor, the at least one region corresponding tothe detected change, selecting the at least one additional measurementresponsive to the candidate points corresponding to the determinedregion, and assigning the selected at least one additional measurementand revising at least one of the measurements, the additionalmeasurement and the plan; (E) wherein the measurements are adjusted bydetermining, in the processor, whether the detected change may affect aseries of wafers, and if so, determining whether to measure at least oneof the wafers in the series of wafers; (F) wherein there is provided aplurality of wafers including the at least one wafer, being provided ina group, and wherein the plan further includes first informationrepresentative of the wafers in the group that are available to bemeasured, and second information representative of the wafers in thegroup that are to be measured under the plan; (G) storage of informationrepresentative of measurement results on the at least one wafer, exceptwhen the measurements results indicate a variation in measurement of theat least one wafer and when a fault is detected in the manufacturingprocess; and (H) wherein the sampling plan includes a plurality ofsplines radiating from a center of the at least one wafer, the candidatepoints being distributed along the splines; and a distribution of thecandidate points along the splines being weighted according to a surfacearea of the at least one wafer.
 33. A computer program for measuring atleast one manufacturing characteristic for at least one productmanufactured by a manufacturing process, the computer program stored ona computer-readable medium, comprising: (A) instructions for providinginformation representative of a set of candidate points to be measuredby the manufacturing process on the at least one product; (B)instructions for executing, by the manufacturing process, a plan forperforming measurements on the at least one product to measure the atleast one manufacturing characteristic, the plan defining themeasurements to be made responsive to said set of candidate points; (C)instructions for detecting a change in the manufacturing process, thechange including at least one of: receiving new material in themanufacturing process, detecting a fault in the manufacturing process,detecting a change in a control parameter in the manufacturing process,and detecting a variation in a measurement of the at least one product;and (D) instructions for adjusting the plan for performing measurementsbased on the detected change.
 34. The program of claim 33, furthercomprising instructions, responsive to the detected change, forperforming at least one additional measurement.
 35. The program of claim33, further comprising instructions for adjusting measurements of theplan wafer-to-wafer and/or within-wafer.
 36. The program of claim 33,wherein the product is a semi-conductor wafer and the manufacturingprocess is an automated semi-conductor manufacturing process.
 37. Theprogram of claim 33, wherein the plan further includes informationrepresentative of a metrology recipe.
 38. The program of claim 33,wherein the candidate points are included in a map corresponding to theat least one product.
 39. The program of claim 33, wherein the plan is apre-determined sampling plan.
 40. The program of claim 33, wherein theplan defines at least one region on the product, each of the candidatepoints corresponding to the at least one region.
 41. The program ofclaim 40, wherein adjusting includes determining the at least one regioncorresponding to the detected change, selecting at least one additionalmeasurement responsive to the candidate points corresponding to thedetermined region, assigning the selected at least one additionalmeasurement to be performed under the plan, and revising at least one ofthe measurements, the additional measurement and the plan.
 42. Theprogram of claim 33, wherein adjusting includes determining whether thedetected change may affect a series of products, and if so, determiningwhether to measure at least one of the products in the series ofproducts.
 43. The program of claim 42, wherein there is provided aplurality of products including the at least one product, being providedin a group, and wherein the plan further includes first informationrepresentative of the products in the group that are available to bemeasured, and second information representative of the products in thegroup that are to be measured under the plan.
 44. The program of claim33, further comprising instructions for discarding informationrepresentative of measurement results on the at least one product whenthe measurements results indicate a variation in measurement of the atleast one product and/or when a fault is detected in the manufacturingprocess.
 45. The program of claim 39, wherein the sampling plan includesa plurality of splines radiating from a center of the at least oneproduct, and wherein the candidate points are distributed along thesplines.
 46. The program of claim 45, wherein a distribution of thecandidate points along the splines is weighted according to a surfacearea of the at least one product.
 47. The program of claim 39, whereinthe sampling plan includes a plurality of radially distributed candidatepoints.
 48. A computer-implemented program of measuring at least onemanufacturing characteristic for at least one semi-conductor wafermanufactured by an automated semi-conductor manufacturing process, thecomputer program stored on a computer-readable medium, comprising: (A)instructions for providing information representative of a set ofcandidate points to be measured by the manufacturing process on the atleast one wafer, the set of candidate points being included in a mapcorresponding to the at least one wafer; (B) instructions for executing,by the manufacturing process, a pre-determined sampling plan forperforming measurements on the at least one wafer to measure the atleast one manufacturing characteristic, the plan defining themeasurements to be made responsive to said set of candidate points, andthe plan defining at least one region on the at least one wafer, each ofthe candidate points corresponding to the at least one region; (C)instructions for detecting a change in the manufacturing processresponsive thereto, the change including at least one of: receiving newmaterial in the manufacturing process, detecting a fault in themanufacturing process, detecting a change in a control parameter in themanufacturing process, and detecting a variation in a measurement of theat least one wafer; (D) instructions for adjusting the plan forperforming measurements based on the detected change; (E) whereinadjusting includes determining the at least one region corresponding tothe detected change, selecting the at least one additional measurementresponsive to the candidate points corresponding to the determinedregion, assigning the selected at least one additional measurement, andrevising at least one of the measurements, the additional measurement,and the plan; (F) wherein adjusting includes determining whether thedetected change may affect a series of wafers, and if so, determiningwhether to measure at least one of the wafers in the series of wafers;(G) wherein there is provided a plurality of wafers, including the atleast one wafer, being provided in a group, and wherein the plan furtherincludes first information representative of the wafers in the groupthat are available to be measured, and second information representativeof the wafers in the group that are to be measured under the plan; (H)instructions for discarding information representative of measurementresults on the at least one wafer when the measurements results indicatea variation in measurement of the at least wafer and when a fault isdetected in the manufacturing process; and (I) wherein the sampling planincludes a plurality of splines radiating from a center of at least onewafer, the candidate points being distributed along the splines; and adistribution of the candidate points along the splines is weightedaccording to a surface area of the at least one wafer.
 49. Acomputer-implemented system of measuring at least one manufacturingcharacteristic for at least one manufactured by a manufacturing process,comprising: means for representing a set of candidate points to bemeasured by the manufacturing process on the at least one product; meansfor providing a plan for performing measurements on the at least oneproduct to measure the at least one manufacturing characteristic, theplan defining the measurements to be made responsive to said set ofcandidate points; means for detecting a change in the manufacturingprocess, the change including at least one of: receiving new material inthe manufacturing process, detecting a fault in the manufacturingprocess, detecting a change in a control parameter in the manufacturingprocess, and detecting a variation in a measurement of the at least oneproduct; and means for adjusting, responsive to a detected change, theplan for performing measurements based on the detected change.
 50. Thesystem of claim 49, further comprising means for causing at least oneadditional measurement responsive to the detected change.
 51. The systemof claim 49, wherein the detecting means further includes adjusting themeasurements of the plan wafer-to-wafer and/or within-wafer.
 52. Thesystem of claim 49, wherein the product to be measured is asemi-conductor wafer and the manufacturing process is an automatedsemi-conductor manufacturing process, further comprising at least meansfor performing measurements on said semi-conductor wafer.
 53. The systemof claim 49, wherein the plan further includes informationrepresentative of a metrology recipe.
 54. The system of claim 49,wherein the candidate points are included in a map corresponding to theat least one product.
 55. The system of claim 49, wherein the plan is apre-determined sampling plan.
 56. The system of claim 49, wherein theplan defines at least one region on the product, each of the candidatepoints corresponding to the at least one region.
 57. The system of claim56, wherein adjusting means adjust the measurements by determining, inthe processor, the at least one region corresponding to the detectedchange, selecting at least one additional measurement responsive to thecandidate points corresponding to the determined region, assigning theselected at least one additional measurement to be performed under theplan, and revising at least one of the measurements, the additionalmeasurement and the plan.
 58. The system of claim 49, wherein theadjusting means includes adjusting measurements by determining whetherthe detected change may affect a series of products, and if so,determining whether to measure at least one of the products in theseries of products.
 59. The system of claim 58, wherein there isprovided a plurality of products including the at least one product,being provided in a group, and wherein the plan further includes firstinformation representative of the products in the group that areavailable to be measured, and second information representative of theproducts in the group that are to be measured under the plan.
 60. Thesystem of claim 49, further comprising means for representingmeasurement results on the at least one product, except when themeasurements results indicate a variation in measurement of the at leastone product and/or when a fault is detected in the manufacturingprocess.
 61. The system of claim 55, wherein the sampling plan includesa plurality of splines radiating from a center of the at least oneproduct, and wherein the candidate points are distributed along thesplines
 62. The system of claim 61, wherein a distribution of thecandidate points along the splines is weighted according to a surfacearea of the at least one product.
 63. The system of claim 49, whereinthe sampling plan includes a plurality of radially distributed candidatepoints.